When you insert the disk after Workbench has booted, does it let you browse the files on the disk? If so, then you might be able to manually install it by simply dragging the disk icon onto your hard drive somewhere and looking at the disks s:startup-sequence file to see which file needs to be loaded to load the game. If it needs any assigns you'll soon find out. It's more likely though that the disk will not show up in Workbench other than NDOS: or something, in which case WHDLoad shall come to your rescue should you desire.
